1. Field of the Invention
The present invention relates to heat-generating nanomaterials having a hetero-structure.
2. Description of the Related Art
Nanomaterials have new physiochemical characteristics different from bulk materials due to their minute size. The intensive researches for the nanomaterials permit nanomaterials to be precisely controlled in their composition and shape as well as the size, enabling that the physiochemical properties in a nano-region can be controlled like those in a bulk-region. Using these novel properties, the nanomaterials has been currently utilized in a variety of applications such as catalysts for chemical reactions, fabrication of next generation nanodevices, development of new sources of energy, and cancer diagnosis and therapy in combination with a biomedical science (nano-medicine).
Of them, magnetic nanomaterials generate heat under a magnetic field of high frequency by (a) Brownian relaxation caused by rotation of nanomaterials dispersed in a liquid solution and (b) Neel relaxation caused from energy barrier of internal spin of nanomaterials (E=KV, where K is the anisotropy constant and V is the volume of the nanomaterial) due to their unique magnetic property (J. Mater. Chem., 2004, 14, 2161-2175). Using heat generated thus, the magnetic nanomaterials may be applied to a multitude of heat-generating devices or technologies. Specially, in medical area, heat generated from the magnetic materials under a magnetic field of high frequency has been used in hyperthermia for various diseases and disorders such as cancer.
Heat generated by magnetic nanomaterials may be quantitated by a specific loss power (SLP). As referred to R. E. Rosensweig J. Magn. Magn. Mater. 2002, 252, 370-374, the value of specific loss power was determined according to various factors of materials, in particular a spin anisotropy and a saturation magnetism (Ms).
In this context, various research groups have made intensive studies to develop nanomaterials having higher specific loss power. Up to date, the applicable fields of heat generation using nanomaterials are as follows:
U.S. Pat. No. 7,282,479 discloses a hyperthermia agent for malignant tumors comprising the magnetic fine particles such as ferrite, magnetite or permalloy.
US Pat. Appln. No. 2005-0090732 discloses a targeted thermotherapy using an iron oxide.
U.S. Pat. No. 6,541,039 discloses a hyperthermia method using an iron oxide coated by a silica or polymer.
WO2006/102307 discloses a method for hyperthermia using the magnetic nanoparticle in which a core coated with a noble metal is surrounded by other organic shell, followed by packing with an antibody or a fluorescent material.
However, the nanoparticles disclosed in U.S. Pat. No. 7,282,479 and US Pat. Appln. No. 2005-0090732 are related to a cancer therapy using magnetic nanoparticles with a single structure. In addition, it is one of the purposes of the above-mentioned patents to develop a therapeutic agent for target a cancer by attaching targeting substances to conventional magnetic materials, instead of increasing the specific loss power of magnetic nanoparticles.
In U.S. Pat. No. 6,541,039 and WO2006/102307, the heat-generating nanoparticle coated with multiple shells is provided but the components of shells are unlikely to contribute to enhancement of the specific loss power of magnetic nanoparticles.
The main reason why there is limitations on the increase in the specific loss power of nanoparticles is because most of researches on physiochemical characteristics of nanomaterials is focused on the controlling their size, shape and/or composition of simple structural nanomaterials. Therefore, these nanomaterials with a simple structure have serious limitations in their function or stability. As an alternative to overcome the drawbacks, the hetero-structure nanocomplex has been provided to have a high- and multi-functionality remarkably better than simple structural nanomaterials. For example, CdSe@ZnS (Nano Lett. 2001, 1, 207-211) or CdSe@CdS (J. Am. Chem. Soc. 1997, 119, 7019-7029) nanocomplex has an increased optical property and stability compared to simple structural nanomaterials. In addition, FePt@Fe3O4 (Nano Lett. 2004, 4, 187-190) nanocomplex has novel magnetic properties. As such, the hetero-structure nanocomplex exhibits new optical, magnetic and chemical characteristics due to interactions between its components, not observed in simple structural nanomaterials.
As described above, a number of studies for hyperthermia using magnetic materials have been attempted; however the magnetic nanomaterials used so far had some limitations in the increase of the value of specific loss power due to their restricted physiochemical characteristics. Accordingly, the present invention may be suggested as a new alternative since a hetero-structure nanomaterial in the present invention shows a dramatic heat-generating effect.
Throughout this application, various publications and patents are referred and citations are provided in parentheses. The disclosures of these publications and patents in their entities are hereby incorporated by references into this application in order to fully describe this invention and the state of the art to which this invention pertains.